Re: [Xen-devel] pvops dom0: no sound after boot; possibly causedby swiotlb

[Ronny.Hegewald@xxxxxxxxx]

> I am curious - if you dom0 is 64-bit, does the sound card work? 

Yes with 64-bit pvops-dom0 the sound works fine without any patches.

>> 
>> Ooooh. I completly failed to notice that your dom0 was 32-bit.
>> 
>> But having that there would make the mask always be below
>> 4GB, irregardless if the dom0 is 32 or 64-bit. Which is 
>> exactly what it does on bare-metal. 
><sigh> That is actually incorrect. Looking at the
>dma_alloc_coherent_mask I missed the '!' and thought it would set it
>irregardless of what the previous value was. That is not the case.

No, your first statement was correct. It would always return the same mask for 
32-bit and 64-bit, because of the 32-bitness of the return-variable 'dma_mask'.

So the following patch maybe would be more appropriate?

--- arch/x86/xen/pci-swiotlb.c-org      2010-02-01 23:04:42.000000000 +0100
+++ arch/x86/xen/pci-swiotlb.c  2010-02-04 02:47:17.000000000 +0100
@@ -602,7 +602,11 @@ xen_swiotlb_alloc_coherent(struct device
        ret = (void *)vstart;

        if (hwdev != NULL && hwdev->coherent_dma_mask)
+#ifdef CONFIG_X86_32
+               mask = dma_alloc_coherent_mask(hwdev, flags);
+#else
                mask = hwdev->coherent_dma_mask;
+#endif

        else
                mask = DMA_BIT_MASK(32);

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